James Barker - Academia.edu (original) (raw)
Papers by James Barker
Antioxidants
Recently, nitric oxide (NO) has been reported to increase plant resistance to heavy metal stress.... more Recently, nitric oxide (NO) has been reported to increase plant resistance to heavy metal stress. In this regard, an in vitro tissue culture experiment was conducted to evaluate the role of the NO donor sodium nitroprusside (SNP) in the alleviation of heavy metal toxicity in a bamboo species (Arundinaria pygmaea) under lead (Pb) and cadmium (Cd) toxicity. The treatment included 200 µmol of heavy metals (Pb and Cd) alone and in combination with 200 µM SNP: NO donor, 0.1% Hb, bovine hemoglobin (NO scavenger), and 50 µM L-NAME, N(G)-nitro-L-arginine methyl ester (NO synthase inhibitor) in four replications in comparison to controls. The results demonstrated that the addition of L-NAME and Hb as an NO synthase inhibitor and NO scavenger significantly increased oxidative stress and injured the cell membrane of the bamboo species. The addition of sodium nitroprusside (SNP) for NO synthesis increased antioxidant activity, protein content, photosynthetic properties, plant biomass, and plant...
Northwestern Journal of International Law Business, 1992
reviewing prior drafts of this article. 1 Professor Boss observes: With the advent of more sophis... more reviewing prior drafts of this article. 1 Professor Boss observes: With the advent of more sophisticated technology, our globe is in effect, if not in fact, rapidly shrinking. Thus it is not surprising that international trade is increasingly conducted by the electronic transmission of data in all stages of the transaction, from negotiation through contract formation, performance (e.g., shipment), insurance, and payment.
Journal of the Chemical Society, Dalton Transactions, 1989
Lithiobenzamidine reacts with [Pt(PhCN)2Cl2], in diethyl ether solution, by attack at the carbon ... more Lithiobenzamidine reacts with [Pt(PhCN)2Cl2], in diethyl ether solution, by attack at the carbon of the co-ordinated nitrile to form [Pt{HNC(Ph)NC(Ph)NH}2]. The crystal structure, obtained on the golden-yellow platelets of the toluene crystallate, showed a planar molecule having six-membered metallo-ring systems containing three nitrogen atoms. [Pt{HNC(Ph)NC(Ph)NH}2]·⅔PhMe forms monoclinic crystals [a= 15.468(4), b= 12.576(3), c= 25.206(7)A, β= 117.64°, space group P21/c with six molecules of the complex and four toluenes in each unit cell] in which each planar HNC(Ph)NC(Ph)NH ligand adopts symmetrical σ,σ-attachment through two terminal N atoms The PtN4unit is planar with a mean Pt–N distance of 1.96 A. Carbon–nitrogen distances in the ring system are similar, 1.30(7)A for C–N(C) and 1.36(7)A for C–N(Pt). This complex is markedly different from the product obtained using lithio-t-butylamidine, LiNHC(Bu)NH, and [Pd(PhCN)2Cl2]. The presence of [Pd3L4]+ ions [L = HNC(Ph)NC(But)NH] in the mass spectrum and the low solubility of the material suggest a polymeric structure.
In 1995, Nova Southeastern University (NSU) formed a research group of post graduate students to ... more In 1995, Nova Southeastern University (NSU) formed a research group of post graduate students to study the application of Internet/Web tools for bringing multimedia to the distance learning environment. Scigliano, Levin, and Horne (1995) reported the effort to improve interaction on the NSU distance learning network through some of these new Web tools (e.g. hypertext markup language or HTML). Faculty and students are now authoring with HTML extensively thus developing a nonlinear knowledge base that resides on the NSU server and which facilitates collaborative learning and research. But the very nature of such a collaborative learning environment is that it is not centralized and we see this in the way the Internet is evolving and structured today. Consequently, the multimedia research group formed a special project team to investigate the possibility of distributing the learning environment under a concept known as “server-at-home”. This paper reviews the problems and vision that l...
Science, 1970
Although nothing of direct biologic interest was observed in the sample studied, small shaped gla... more Although nothing of direct biologic interest was observed in the sample studied, small shaped glass particles and glazed pits resemble objects which elsewhere have been described as fossils. These features, although nonbiological, do bear on processes of lunar weathering and outgassing. The glazed pits are impact features. Fusion of their surfaces released gases. Electron microscopy of the glasses, pits, and angular microfractured mineral grains indicates a prevalence of destructive weathering processes-thermal expansion and contraction, abrasion by by-passing particles, and, of course, impact. ous at room temperature.
The Pediatric Infectious Disease Journal, 1990
Page 1. I'cdiatr liiliTt I )iv .1. H:'JS"i 1Í.VI. PUH! IISHl-.'tlilih '.... more Page 1. I'cdiatr liiliTt I )iv .1. H:'JS"i 1Í.VI. PUH! IISHl-.'tlilih '.Ml SII'J.IIII <l Cupyriiiht ' 1ÍIÍHI hv Williams \ Wilkins Viil. il. Nu. -I l'niilnl m I '.SA Primary neonatal herpes simplex virus pneumonia JAMES A. HARKER, MI), SCOTT I). MCLEAN ...
Organic Geochemistry, 1990
Energy & Fuels, 2011
ABSTRACT
Chemosphere, 2010
The reactivity of permanganate towards polycyclic aromatics hydrocarbons (PAHs) is well known but... more The reactivity of permanganate towards polycyclic aromatics hydrocarbons (PAHs) is well known but little kinetic information is available. This study investigated the oxidation kinetics of a selected group of coal tar creosote compounds and alkylbenzenes in water using permanganate, and the correlation between compound reactivity and physical/chemical properties. The oxidation of naphthalene, phenanthrene, chrysene, 1-methylnaphthalene, 2-methylnaphthalene, acenaphthene, fluorene, carbazole isopropylbenzene, ethylbenzene and methylbenzene closely followed pseudo first-order reaction kinetics. The oxidation of pyrene was initially very rapid and did not follow pseudo first-order kinetics at early times. Fluoranthene was only partially oxidized and the oxidation of anthracene was too fast to be captured. Biphenyl, dibenzofuran, benzene and tert-butylbenzene were non-reactive under the study conditions. The oxidation rate was shown to increase with increasing number of polycyclic rings because less energy is required to overcome the aromatic character of a polycyclic ring than is required for benzene. Thus the rate of oxidation increased in the series naphthalene < phenanthrene < pyrene. The rate of side chain reactivity is controlled by the C-H bond strength. For the alkyl substituted benzenes an excellent correlation was observed between the reaction rate coefficients and bond dissociation energies, but for the substituted PAHs the relationship was poor. A trend was found between the reaction rate coefficients and the calculated heats of complexation indicating that significant ring oxidation occurred in addition to side chain oxidation. Clar's aromatic sextet theory was used to predict the relative stability of arenes towards ring oxidation by permanganate.
Oxygenates are typically added to gasoline aiming to decrease greenhouse gas emissions. MTBE used... more Oxygenates are typically added to gasoline aiming to decrease greenhouse gas emissions. MTBE used to be the most common additive in North America, but it is increasingly being replaced by ethanol. In the events of accidental spills, besides presenting an environmental concern itself, oxygenates might change the behaviour of the gasoline compounds in the subsurface. Both MTBE and ethanol are extremely soluble, and therefore are expected to behave differently than most of the gasoline compounds. Previous lab experiments indicated that ethanol stays mainly in the capillary fringe, being transported above the water table along with cosolubilized hydrocarbons. Although this has been demonstrated at lab scale, few field tests have evaluated transport in the capillary fringe, largely due to difficulties associated with sampling. To investigate the fate of MTBE, ethanol and gasoline in the vadose zone, a controlled release of gasoline with 10% ethanol and 4.5% MTBE was conducted at the shallow unconfined sandy aquifer in CFB-Borden, Ontario. Groundwater concentrations above and below the water table were monitored using multilevel wells constructed with porous suction samplers, positioned downgradient the source zone in a row perpendicular to groundwater flow. Soil cores and gas samples were also collected to complement the monitoring. Horizontal transport in the capillary fringe was found to be significant, as indicated by high concentrations in the groundwater above the water table for all compounds tested. Ethanol and MTBE partitioned quickly from the NAPL to the pore water due to their high solubilities. However, ethanol horizontal transport was delayed in comparison to MTBE, assumed to behave as a tracer. Soil cores in the source zone after the spill indicate that ethanol was being retained in the unsaturated zone, above the zone of high hydrocarbons saturation. Water table oscillation between 70 and 20cm bgs resulted in spreading of the gasoline in the unsaturated zone, while ethanol peak concentrations were always found at the first 25cm. The retention of ethanol in the unsaturated zone likely caused delay in its horizontal transport.
We have identified crystal growth conditions in gas-source molecular beam epitaxy (MBE) that lead... more We have identified crystal growth conditions in gas-source molecular beam epitaxy (MBE) that lead to spontaneous formation of GaN nanowires with high aspect ratio on Si (1 1 1) substrates. The nanowires were oriented along the GaN c-axis and normal to the substrate surface. Unlike in many other reports of GaN nanowire growth, no metal catalysts were used. Low growth rates at substrate temperatures near 820 1C were combined with high nitrogen flux (partially dissociated with RF plasma excitation) to form well-separated GaN wires with diameters from 50 to 250 nm in diameter and lengths ranging from 2 to 7 mm. The nanowires grew out of an irregular matrix layer containing deep faceted holes. X-ray diffraction indicated that the wires were fully relaxed and aligned to the silicon substrate. The growth morphology was strongly affected by the presence of Al and Be. The changes suggest that surface diffusion is a primary driving force in the growth of GaN nanowires with MBE.
Journal of Contaminant …, 2003
Mainly due to intrinsic biodegradation, monitored natural attenuation can be an effective and ine... more Mainly due to intrinsic biodegradation, monitored natural attenuation can be an effective and inexpensive remediation strategy at petroleum release sites. However, gasoline additives such as methyl tert-butyl ether (MTBE) can jeopardize this strategy because these compounds ...
Ground Water Monitoring & …, 1998
Three sampling rounds were carried out (November 1995; July/August 1996; November 1996). Samples ... more Three sampling rounds were carried out (November 1995; July/August 1996; November 1996). Samples obtained in the first sampling round were analyzed for MTBE at a commercial laboratory using US EPA SW-846 Method 8240. Beginning in 1996, samples were ana- ...
Antioxidants
Recently, nitric oxide (NO) has been reported to increase plant resistance to heavy metal stress.... more Recently, nitric oxide (NO) has been reported to increase plant resistance to heavy metal stress. In this regard, an in vitro tissue culture experiment was conducted to evaluate the role of the NO donor sodium nitroprusside (SNP) in the alleviation of heavy metal toxicity in a bamboo species (Arundinaria pygmaea) under lead (Pb) and cadmium (Cd) toxicity. The treatment included 200 µmol of heavy metals (Pb and Cd) alone and in combination with 200 µM SNP: NO donor, 0.1% Hb, bovine hemoglobin (NO scavenger), and 50 µM L-NAME, N(G)-nitro-L-arginine methyl ester (NO synthase inhibitor) in four replications in comparison to controls. The results demonstrated that the addition of L-NAME and Hb as an NO synthase inhibitor and NO scavenger significantly increased oxidative stress and injured the cell membrane of the bamboo species. The addition of sodium nitroprusside (SNP) for NO synthesis increased antioxidant activity, protein content, photosynthetic properties, plant biomass, and plant...
Northwestern Journal of International Law Business, 1992
reviewing prior drafts of this article. 1 Professor Boss observes: With the advent of more sophis... more reviewing prior drafts of this article. 1 Professor Boss observes: With the advent of more sophisticated technology, our globe is in effect, if not in fact, rapidly shrinking. Thus it is not surprising that international trade is increasingly conducted by the electronic transmission of data in all stages of the transaction, from negotiation through contract formation, performance (e.g., shipment), insurance, and payment.
Journal of the Chemical Society, Dalton Transactions, 1989
Lithiobenzamidine reacts with [Pt(PhCN)2Cl2], in diethyl ether solution, by attack at the carbon ... more Lithiobenzamidine reacts with [Pt(PhCN)2Cl2], in diethyl ether solution, by attack at the carbon of the co-ordinated nitrile to form [Pt{HNC(Ph)NC(Ph)NH}2]. The crystal structure, obtained on the golden-yellow platelets of the toluene crystallate, showed a planar molecule having six-membered metallo-ring systems containing three nitrogen atoms. [Pt{HNC(Ph)NC(Ph)NH}2]·⅔PhMe forms monoclinic crystals [a= 15.468(4), b= 12.576(3), c= 25.206(7)A, β= 117.64°, space group P21/c with six molecules of the complex and four toluenes in each unit cell] in which each planar HNC(Ph)NC(Ph)NH ligand adopts symmetrical σ,σ-attachment through two terminal N atoms The PtN4unit is planar with a mean Pt–N distance of 1.96 A. Carbon–nitrogen distances in the ring system are similar, 1.30(7)A for C–N(C) and 1.36(7)A for C–N(Pt). This complex is markedly different from the product obtained using lithio-t-butylamidine, LiNHC(Bu)NH, and [Pd(PhCN)2Cl2]. The presence of [Pd3L4]+ ions [L = HNC(Ph)NC(But)NH] in the mass spectrum and the low solubility of the material suggest a polymeric structure.
In 1995, Nova Southeastern University (NSU) formed a research group of post graduate students to ... more In 1995, Nova Southeastern University (NSU) formed a research group of post graduate students to study the application of Internet/Web tools for bringing multimedia to the distance learning environment. Scigliano, Levin, and Horne (1995) reported the effort to improve interaction on the NSU distance learning network through some of these new Web tools (e.g. hypertext markup language or HTML). Faculty and students are now authoring with HTML extensively thus developing a nonlinear knowledge base that resides on the NSU server and which facilitates collaborative learning and research. But the very nature of such a collaborative learning environment is that it is not centralized and we see this in the way the Internet is evolving and structured today. Consequently, the multimedia research group formed a special project team to investigate the possibility of distributing the learning environment under a concept known as “server-at-home”. This paper reviews the problems and vision that l...
Science, 1970
Although nothing of direct biologic interest was observed in the sample studied, small shaped gla... more Although nothing of direct biologic interest was observed in the sample studied, small shaped glass particles and glazed pits resemble objects which elsewhere have been described as fossils. These features, although nonbiological, do bear on processes of lunar weathering and outgassing. The glazed pits are impact features. Fusion of their surfaces released gases. Electron microscopy of the glasses, pits, and angular microfractured mineral grains indicates a prevalence of destructive weathering processes-thermal expansion and contraction, abrasion by by-passing particles, and, of course, impact. ous at room temperature.
The Pediatric Infectious Disease Journal, 1990
Page 1. I'cdiatr liiliTt I )iv .1. H:'JS"i 1Í.VI. PUH! IISHl-.'tlilih '.... more Page 1. I'cdiatr liiliTt I )iv .1. H:'JS"i 1Í.VI. PUH! IISHl-.'tlilih '.Ml SII'J.IIII <l Cupyriiiht ' 1ÍIÍHI hv Williams \ Wilkins Viil. il. Nu. -I l'niilnl m I '.SA Primary neonatal herpes simplex virus pneumonia JAMES A. HARKER, MI), SCOTT I). MCLEAN ...
Organic Geochemistry, 1990
Energy & Fuels, 2011
ABSTRACT
Chemosphere, 2010
The reactivity of permanganate towards polycyclic aromatics hydrocarbons (PAHs) is well known but... more The reactivity of permanganate towards polycyclic aromatics hydrocarbons (PAHs) is well known but little kinetic information is available. This study investigated the oxidation kinetics of a selected group of coal tar creosote compounds and alkylbenzenes in water using permanganate, and the correlation between compound reactivity and physical/chemical properties. The oxidation of naphthalene, phenanthrene, chrysene, 1-methylnaphthalene, 2-methylnaphthalene, acenaphthene, fluorene, carbazole isopropylbenzene, ethylbenzene and methylbenzene closely followed pseudo first-order reaction kinetics. The oxidation of pyrene was initially very rapid and did not follow pseudo first-order kinetics at early times. Fluoranthene was only partially oxidized and the oxidation of anthracene was too fast to be captured. Biphenyl, dibenzofuran, benzene and tert-butylbenzene were non-reactive under the study conditions. The oxidation rate was shown to increase with increasing number of polycyclic rings because less energy is required to overcome the aromatic character of a polycyclic ring than is required for benzene. Thus the rate of oxidation increased in the series naphthalene < phenanthrene < pyrene. The rate of side chain reactivity is controlled by the C-H bond strength. For the alkyl substituted benzenes an excellent correlation was observed between the reaction rate coefficients and bond dissociation energies, but for the substituted PAHs the relationship was poor. A trend was found between the reaction rate coefficients and the calculated heats of complexation indicating that significant ring oxidation occurred in addition to side chain oxidation. Clar's aromatic sextet theory was used to predict the relative stability of arenes towards ring oxidation by permanganate.
Oxygenates are typically added to gasoline aiming to decrease greenhouse gas emissions. MTBE used... more Oxygenates are typically added to gasoline aiming to decrease greenhouse gas emissions. MTBE used to be the most common additive in North America, but it is increasingly being replaced by ethanol. In the events of accidental spills, besides presenting an environmental concern itself, oxygenates might change the behaviour of the gasoline compounds in the subsurface. Both MTBE and ethanol are extremely soluble, and therefore are expected to behave differently than most of the gasoline compounds. Previous lab experiments indicated that ethanol stays mainly in the capillary fringe, being transported above the water table along with cosolubilized hydrocarbons. Although this has been demonstrated at lab scale, few field tests have evaluated transport in the capillary fringe, largely due to difficulties associated with sampling. To investigate the fate of MTBE, ethanol and gasoline in the vadose zone, a controlled release of gasoline with 10% ethanol and 4.5% MTBE was conducted at the shallow unconfined sandy aquifer in CFB-Borden, Ontario. Groundwater concentrations above and below the water table were monitored using multilevel wells constructed with porous suction samplers, positioned downgradient the source zone in a row perpendicular to groundwater flow. Soil cores and gas samples were also collected to complement the monitoring. Horizontal transport in the capillary fringe was found to be significant, as indicated by high concentrations in the groundwater above the water table for all compounds tested. Ethanol and MTBE partitioned quickly from the NAPL to the pore water due to their high solubilities. However, ethanol horizontal transport was delayed in comparison to MTBE, assumed to behave as a tracer. Soil cores in the source zone after the spill indicate that ethanol was being retained in the unsaturated zone, above the zone of high hydrocarbons saturation. Water table oscillation between 70 and 20cm bgs resulted in spreading of the gasoline in the unsaturated zone, while ethanol peak concentrations were always found at the first 25cm. The retention of ethanol in the unsaturated zone likely caused delay in its horizontal transport.
We have identified crystal growth conditions in gas-source molecular beam epitaxy (MBE) that lead... more We have identified crystal growth conditions in gas-source molecular beam epitaxy (MBE) that lead to spontaneous formation of GaN nanowires with high aspect ratio on Si (1 1 1) substrates. The nanowires were oriented along the GaN c-axis and normal to the substrate surface. Unlike in many other reports of GaN nanowire growth, no metal catalysts were used. Low growth rates at substrate temperatures near 820 1C were combined with high nitrogen flux (partially dissociated with RF plasma excitation) to form well-separated GaN wires with diameters from 50 to 250 nm in diameter and lengths ranging from 2 to 7 mm. The nanowires grew out of an irregular matrix layer containing deep faceted holes. X-ray diffraction indicated that the wires were fully relaxed and aligned to the silicon substrate. The growth morphology was strongly affected by the presence of Al and Be. The changes suggest that surface diffusion is a primary driving force in the growth of GaN nanowires with MBE.
Journal of Contaminant …, 2003
Mainly due to intrinsic biodegradation, monitored natural attenuation can be an effective and ine... more Mainly due to intrinsic biodegradation, monitored natural attenuation can be an effective and inexpensive remediation strategy at petroleum release sites. However, gasoline additives such as methyl tert-butyl ether (MTBE) can jeopardize this strategy because these compounds ...
Ground Water Monitoring & …, 1998
Three sampling rounds were carried out (November 1995; July/August 1996; November 1996). Samples ... more Three sampling rounds were carried out (November 1995; July/August 1996; November 1996). Samples obtained in the first sampling round were analyzed for MTBE at a commercial laboratory using US EPA SW-846 Method 8240. Beginning in 1996, samples were ana- ...